The present invention relates generally to apparatus for reinforcing rock structure and, more particularly, relates to bolt-like fixing assemblies including an elongate structure one end of which is fixed within a bore formed in a rock, and means for fixing the other end of the elongate structure to the rock surface.
Rock bolting will be understood by those skilled in the art as constituting a measure undertaken to increase the strength of rock and/or to insure the stability of a rock structure. Rock bolting entails the use of rock bolts which will be understood as including a rod adapted to be situated within a bore drilled in the rock and whose purpose is to fix boulders or large rocks to intact rock and/or to prevent the separation of adjacent boulders. Thus, generally, rock bolting is used to achieve reinforcement of rock structure.
The technique of rock bolting is generally performed as follows. So-called bulb steel rods having a diameter of, for example, 25 mm are used as the rock bolts. A thread is machined on one end of the bulb steel rod whereupon the rock bolt is inserted into a bore previously drilled in the rock whereupon a washer is tightened against the surface of the rock by a threaded nut thereby preventing the boulder from falling. The other end of the rock bolt is fixed within the bore of the rock either by grouting or, in the case of an active rock bolt, by means of a wedge. One example wherein rock bolting is used is in the construction of a conventional rock cistern for crude petroleum storage which will require about 20,000 rock bolts.
The conventional arrangement for strengthening rock structure described above, however, has several drawbacks. For example, the rock bolts are exceedingly expensive and, secondly, the use of rock bolts having various lengths is inconvenient. Thirdly, the installation or mounting of the rocks involves several time consuming steps and, fourthly, the machined thread of the rock bolt will inherently reduce the strength of the fixation. Moreover, in the case of a passive rock bolt, the possibility of after-tightening is not required.